The present invention relates generally to electrical testing devices and, more particularly to hand-held devices for testing electrical circuits, wires and the like.
Prior electrical testing devices include single function test devices. These devices typically include a single probe needle or the like extending from one end of the device and a single lead wire extending from the other end of the device. A clip, such as an alligator clip is typically joined to the lead wire and the clip is typically connected to a ground. Thus, when a circuit is probed by the probe needle, a two point connection to the circuit is established.
There are problems with these single function test devices. First, it is often difficult to tell whether the connection to the ground is a good connection. Often, there may be paint, corrosion, rust, etc. built up on the ground and this could prevent good contact between the clip and the ground. In some of these single function test devices it is difficult to distinguish between an open circuit and a grounded circuit. Second, the two point connection of these single function test devices can only give an indication of one circuit condition at a time.
Other known devices include probes for high speed computer applications and oscilloscopes which are also used to measure a signal. These devices are complicated to understand. They also require time consuming hook-up, and expensive equipment generally impractical for use by an automotive technician.
The present invention is designed to check the automotive grade on electronic signals, to be easy to apply, to be relatively inexpensive, and to be easy to interpret output results from the tester. The present invention would be practically useful in checking the frequencies and duty cycle signals from on-board computers or frequency generators. The present invention uses electronic circuitry to detect a changing voltage condition where the voltage signal is changing from the zero voltage state, to the zero voltage state, or is passing through the zero voltage state.
The present invention provides a circuit testing device comprising a body having first and second ends, the body having an electrical circuit or other circuit means contained therein, a probe communicating with the electrical circuit means and extending from the first end of the body, a first power lead having a first end communicating with the electrical circuit means and extending from the second end of the body, a second power lead having a first end communicating with the electrical circuit means and extending from the second end of the body, and preferably a third power lead having a first end communicating with the electrical circuit means and extending from the second end of the body.
In one preferred embodiment of the invention a method exists for measuring low voltage and pulse signals of a test element such as a circuit or wire, comprising the steps of connecting a first lead extending from an electrical circuit of a polarity testing device to a power source, connecting a second lead extending from the electrical circuit testing device to a ground source, and contacting a probe extending from the electrical circuit of the polarity device with a circuit or wire to determine the polarity of the circuit or wire.
Another preferred feature of the present invention is the ability to test more than one circuit condition at a given time. Other principal features and advantages of the present invention will become apparent to those skilled in the art upon review of the following detailed description, claims, and drawings.